page_title: Polymer capacitor
section_title: Polythiopene PEDOT and PEDOT:PSS
hierarchical_section_title: Polymer capacitor / Electrolytic capacitors - basics / Electrolytes / Polythiopene PEDOT and PEDOT:PSS
caption_attribution_description: English: Structure of PEDOT:PSS
context_page_description: A polymer capacitor, or more accurately a polymer electrolytic capacitor, is an electrolytic capacitor with a solid electrolyte of a conductive polymer. There are four different types:
  Polymer tantalum electrolytic capacitor
  Polymer aluminum electrolytic capacitor
  Hybrid polymer capacitor
  Polymer niobium electrolytic capacitors
  Polymer Ta-e-caps are available in rectangular surface-mounted device chip style. Polymer Al-e-caps and hybrid polymer Al-e-caps are available in rectangular surface-mounted device chip style, in cylindrical SMDs style or as radial leaded versions.
  Polymer electrolytic capacitors are characterized by particularly low internal equivalent series resistances and high ripple current ratings. Their electrical parameters have similar temperature dependence, reliability and service life compared to solid tantalum capacitors, but have a much better temperature dependence and a considerably longer service life than aluminum electrolytic capacitors with non-solid electrolytes. In general polymer e-caps have a higher leakage current rating than the other solid or non-solid electrolytic capacitors.
context_section_description: Poly(3,4-ethylenedioxythiophene), abbreviated PEDOT or PEDT  is a conducting polymer based on 3,4-ethylenedioxythiophene or EDOT monomer. PEDOT is polarized by the oxidation of EDOT with catalytic amounts of iron (III) sulfate. The re-oxidation of iron is given by Sodium persulfate. Advantages of PEDOT are optical transparency in its conducting state, non toxic, stable up to temperatures of 280 °C and a conductivity up to 500 S/m. Its heat resistance allows polymer capacitors to be manufactured that withstand the higher temperatures required for lead-free soldering. Additional this capacitors have better ESR values as polymer e-caps with PPy electrolyte.
  The difficult methods of in situ polymerization of PEDOT in the anodes of the capacitors initially were at first the same as with polypyrrole. This changed with the development of pre-polymerized dispersions of PEDOT in which the capacitor anodes simple could be dipped and then dried at room temperature. For this purpose, the PEDOT chemicals  is added with sodium polystyrene sulfonate (PSS) and dissolved in water. The complete polymer layer on the dielectric is then composed of pre-polymerized particles from the dispersion. These dispersions are known as PEDOT: PSS,  trade names Baytron P® and Clevios™, protecting PEDOT's valuable properties.
  PEDOT:PSS dispersions are available in different variants. For capacitors with high capacitance values with high-roughened aluminum anode foils or fine-grained tantalum powders, dispersions having very small particle sizes are offered. The average size of these pre-polymerized particles is about 30 nm, small enough to penetrate the finest anode capillaries. Another variant of a PEDOT:PSS dispersion has been developed with larger pre-polymerized particles leading to a relatively thick polymer layer in order to make an enveloping protection of the capacitive cell of rectangular Ta and Al polymer capacitors against mechanical and electrical stress.
  With PEDOT:PSS dispersions produced polymer aluminum electrolytic capacitors are well suited to reach higher rated voltage values of 200 V and 250 V. In addition, the leakage current values of the polymer electrolytic capacitors, which are produced with these dispersions, are significantly lower than for polymer capacitors having in-situ polymerized polymer layers.. Beneath to the better ESR values, higher temperature stability and lower leakage current values, however, the ease of manufacture of polymer capacitors with the pre-polymerized PEDOT:PSS dispersions, which in already only three dips of immersion have an almost complete coverage of the dielectric with a conducting polymer layer. This approach significantly has reduced production costs.
caption: Structural formula of PEDOT:PSS
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